On 10/21/26 22:16, Val Packett wrote: > > On 10/21/26 10:43 AM, Christian König wrote: >> [..] >>> The buffer lifecycle coordination we need this for applies to KVM as well >>> and it generally doesn't make sense to have this as a provider-specific >>> thing since it's not related to the provider in any way, it's just >>> something we want from dmabufs in general. >> I wouldn't put that on the DMA-buf file descriptor where basically anybody >> can mess with it. That is just an recipe for trouble. >> >> The better approach seems to be putting it into the udmabuf_ioctl(), so that >> from the very beginning you add the eventfd which signals when the udmabuf >> is released. >> >> If we need that for more implementations than just udmabuf, we can >> potentially add it to dma_buf_export_info so that exporters can provide the >> eventfd file descriptor directly on creation. > > Well, we already need it with both udmabuf and gntdev-dmabuf.. > > Involving the exporter sounds really annoying when it's not something > exporter dependent really.. What if the policy is just "only one eventfd > ever" i.e. the first call of the ioctl succeeds but later calls on the same > dmabuf return an error?
No, exactly that is what I'm trying to avoid. Nobody except the original creater should be able to insert an eventfd here. Regards, Christian. > That should remove the concern about one user messing with another's events > (and avoid the concurrent replacement issue sashiko-bot warned about).. > > Thanks, > ~val >
